JAVA-select structure

JAVA-select structure

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if radio structure

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import java.util.Scanner;

public class ifDemo1 {
    
    
    public static void main(String[] args) {
    
    
        Scanner scanner = new Scanner(System.in);

        System.out.println("请输入内容:");
        String s =scanner.nextLine();

        //equals:判断字符串是否相等
        if (s.equals("Hello")){
    
    
            System.out.println(s);
        }
        System.out.println("End");
    }
}

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if double selection structure and

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import java.util.Scanner;

public class ifDemo2 {
    
    
    public static void main(String[] args) {
    
    
        //考试分数大于60就是及格，小于60就不及格。
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入成绩：");
        int score=scanner.nextInt();

        if(score>60){
    
    
            System.out.println("及格");
        }
        else {
    
    
            System.out.println("不及格");
        }
        scanner.close();

    }
}

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if multiple selection structure

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import java.util.Scanner;

public class ifDemo3 {
    
    



        public static void main(String[] args) {
    
    
            //考试分数大于60就是及格，小于60就不及格。
            Scanner scanner = new Scanner(System.in);
            System.out.println("请输入成绩：");
            int score=scanner.nextInt();

            if(score==100){
    
    
                System.out.println("max");
            }
            else if(score<100&&score>=90){
    
    
                System.out.println("A");
            }else if(score<90&&score>=80){
    
    
                System.out.println("B");
            }else if(score<80&&score>=60){
    
    
                System.out.println("C");
            }else if(score<60&&score>=0){
    
    
                System.out.println("E");
            }else{
    
    
                System.out.println("成绩不合法");
            }
            scanner.close();


    }

}

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Nested if structure

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import java.util.Scanner;

public class ifDemo4 {
    
    
    public static void main(String[] args) {
    
    
        Scanner scanner = new Scanner(System.in);
        int mun =scanner.nextInt();

        if(mun<50){
    
    
            System.out.println("<50");
            if (mun<25){
    
    
                System.out.println("<25");
            }
        }
        else if (mun>50){
    
    
            System.out.println(">50");
            if (mun>75){
    
    
                System.out.println(">75");
            }
        }
    }
}

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switch multiple selection structure

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public class switchDemo1 {
    
    
    public static void main(String[] args) {
    
    
        char grade='D';

        switch (grade){
    
    
            case 'A':
                System.out.println("A");
                break;
            case 'B':
                System.out.println("B");
                break;
            default:
                System.out.println("其他");

        }
    }
}